So I figured it out. It seems that this issue is not about tomcat only, but anything related to java on VPS with one virtual core

Also, not only java execution but java compiler too. When compiling java, sometimes (randomly) i have a error reported from .cpp file (java source?) about lock/unlock function failed, related to multithreading.

After requesting VPS support to divide my one virtual 1Ghz CPU to two cores with 0.5Ghz each, tomcat runs without problems